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><A
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>4.9. Teletext Interface</A
></H1
><P
>This interface aims at devices receiving and demodulating
Teletext data [<A
HREF="b17127.htm#ETS300706"
><ABBR
CLASS="ABBREV"
>ETS&nbsp;300&nbsp;706</ABBR
></A
>, <A
HREF="b17127.htm#ITU653"
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>ITU&nbsp;BT.653</ABBR
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>], evaluating the
Teletext packages and storing formatted pages in cache memory. Such
devices are usually implemented as microcontrollers with serial
interface (I<SUP
>2</SUP
>C) and can be found on older
TV cards, dedicated Teletext decoding cards and home-brew devices
connected to the PC parallel port.</P
><P
>The Teletext API was designed by Martin Buck. It is defined in
the kernel header file <TT
CLASS="FILENAME"
>linux/videotext.h</TT
>, the
specification is available from <A
HREF="http://home.pages.de/~videotext/"
TARGET="_top"
>http://home.pages.de/~videotext/</A
>. (Videotext is the name of
the German public television Teletext service.) Conventional character
device file names are <TT
CLASS="FILENAME"
>/dev/vtx</TT
> and
<TT
CLASS="FILENAME"
>/dev/vttuner</TT
>, with device number 83, 0 and 83, 16
respectively. A similar interface exists for the Philips SAA5249
Teletext decoder [specification?] with character device file names
<TT
CLASS="FILENAME"
>/dev/tlkN</TT
>, device number 102, N.</P
><P
>Eventually the Teletext API was integrated into the V4L API
with character device file names <TT
CLASS="FILENAME"
>/dev/vtx0</TT
> to
<TT
CLASS="FILENAME"
>/dev/vtx31</TT
>, device major number 81, minor numbers
192 to 223. For reference the V4L Teletext API specification is
reproduced here in full: "Teletext interfaces talk the existing VTX
API." Teletext devices with major number 83 and 102 will be removed in
Linux 2.6.</P
><P
>There are no plans to replace the Teletext API or to integrate
it into V4L2. Please write to the Video4Linux mailing list: <A
HREF="https://listman.redhat.com/mailman/listinfo/video4linux-list"
TARGET="_top"
>https://listman.redhat.com/mailman/listinfo/video4linux-list</A
>
when the need arises.</P
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